HCR Lateral Flow Assays for Amplified Instrument-Free At-Home SARS-CoV-2 Testing
The lateral flow assay format enables rapid, instrument-free, at-home testing for SARS-CoV-2. Due to the absence of signal amplification, this simplicity comes at a cost in sensitivity. Here, we enhance sensitivity by developing an amplified lateral flow assay that incorporates isothermal, enzyme-free signal amplification based on the mechanism of hybridization chain reaction (HCR). The simplicity of the user experience is maintained using a disposable 3-channel lateral flow device to automatically deliver reagents to the test region in three successive stages without user interaction. To perform a test, the user loads the sample, closes the device, and reads the result by eye after 60 minutes. Detecting gamma-irradiated SARS-CoV-2 virions in a mixture of saliva and extraction buffer, the current amplified HCR lateral flow assay achieves a limit of detection of 200 copies/L using available antibodies to target the SARS-CoV-2 nucleocapsid protein. By comparison, five commercial unamplified lateral flow assays that use proprietary antibodies exhibit limits of detection of 500 copies/L, 1000 copies/L, 2000 copies/L, 2000 copies/L, and 20,000 copies/L. By swapping out antibody probes to target different pathogens, amplified HCR lateral flow assays offer a platform for simple, rapid, and sensitive at-home testing for infectious disease. As an alternative to viral protein detection, we further introduce an HCR lateral flow assay for viral RNA detection. HCR lateral flow assayO_LIAmplified C_LIO_LIInstrument-free C_LIO_LIAt-home C_LIO_LI60 min C_LIO_LINaked eye C_LIO_LISARS-CoV-2 C_LIO_LI200 copies/L C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=166 SRC="FIGDIR/small/508442v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@a04874org.highwire.dtl.DTLVardef@f4ba0borg.highwire.dtl.DTLVardef@e2445corg.highwire.dtl.DTLVardef@f63411_HPS_FORMAT_FIGEXP M_FIG C_FIG